Solutions to Saturday Mac riddles 25

I hope that you enjoyed Saturday’s Mac Riddles, episode 25. Here are my solutions to them.

1: Keynote
Every June I start proceedings (the Keynote at WWDC), the first in the scale (the musical keynote), as I’m sure you love me more than an electrical socket (PowerPoint). What am I?

2: Terminal
I might be your last (terminal) resort, or your favourite destination (travel terminal), where you’ll come for my hard external covering (shell). What am I?

3: I have four 4 TB drives in my RAID system, which provides a total of 8 TB of usable storage. Which of the standard (single, non-nested) RAID levels am I using? Answer: 6.
RAID level 6 uses block-level striping with double distributed parity to enable the set to withstand simultaneous failure of two of the drives. For n drives, it provides (1 – 2/n) of the original storage as usable. With four drives, that is (1 – 2/4) = 0.5, that is just half, in this case 8 out of the original 16 TB. Its fault tolerance is excellent, but comes at a significant cost.

I look forward to your putting alternative cases.